Device for intercoupling singleended and double-ended circuits



May 23, 1950 GUANELLA 2,509,057

, G. DEVICE FOR INTERCOUPLING SINGLE-ENDED AND DOUBLE-ENDED CIRCUITSOriginal Filed Nov. 27, 1943 INVENTOR.

' fiu/otcu/ quanella BY h/ flag ATTORNEY Patented May 23, 1950 DEVICEFOR INTERCOUPLING SINGLE- ENDED AND DOUBLE-ENDED CIRCUITS GustavGuanella, Zurich, Switzerland, assignor to Radio Patents Corporation,New York, N. Y., a corporation of New York Original applicationNovember'27, 1943, Serial No. 512,069. Divided and this application June6, 1945, Serial No. 597,821.

October 8, 1942 In Switzerland Section 1, Public Law 690, August '8,1946 Patent expires October 8, 1962 This application is a division of myabandoned application Serial No. 512,069, filed November 27,

The present invention relates to an arrangement for transferring highfrequency energy from a symmetrical or double-ended-circuit to anunsymmetrical or single-ended circuit and vice 'versa, the object of theinvention being the provision of a device of this type which is simplein construction and efiicient in operation, which requires little space,which can be easily adapted to suit existing conditions and practicalrequirements and which will insure a maximum of energy transfer betweensaid circuits.

The invention will become further apparent from the following detaileddescription taken in reference to the accompanying drawing forming partof this specification and wherein:

Figure 1 shows a spirally wound two-wire transmission line serving as anintercoupling element in accordance with the invention;

Figure 2 shows a coupling line according to Figure 1 connecting asymmetrical input circuit with an unsymmetrical output circuit; and

Figure 3 shows a modified construction of a transmission coupling lineconstructed in accordance with the principle of the invention.

Referring to Figure 1, the conductors l and 2 of a length at least equalto a quarter of the length of the operating wave are wound in an axiallysymmetrical manner in the form of a double spiral upon an insulatingbody 3. If the oscillation currents of the coil system are exactly inopposite phase, as indicated by the full arrows, the magnetic fieldsproduced by these currents neutralize each other and the coil axis haspractically no field. The coil system thus no longer has the characterof an inductance. If, however, the currents are in phase, as indicatedby broken arrows, the coil system represents a considerable reactance;that is to say oscillations of the same phase are to a great extentsuppressed. A coil according to Figure 1 may for instance be used forartificially extending an elec tric two-wire line.

If a double threaded coil according to Figure l is connected to a singleended or unsymmetrical load or consumer, the current passing through thecoil may be symmetrized in accordance with the present invention. Thus,Figure 2 shows an arrangement wherein a push-pull vacuum tube circuit 6having output terminals I I and I2 which supply a voltage symmetricalwith respect to ground, is connected to a single-ended load circuit inthe form of a concentric high frequency 2 Claims. (Cl. 178- 14) cable Ihaving input terminals l3 and 14, of which the former connected to theouter concentric conductor is usually at ground potential. Foroscillations with opposite phases (full arrows) the coil system 8represents a transmission line of definite length. For oscillationsoccurring in phase (broken arrows), system 8 represents a considerableinductance so that these are not transmitted. Even if the output end ofthe line has one pole grounded, only currents of opposite phase mayflow. A symmetrical loading of the input tubes is thus obtained despitethe unsymmetrical earthing of the cable 1. The symmetrising of thecurrents effected by the system causes the current i1 through thecentral conductor to be exactly equal and of opposite phase to thecurrent 2'2 through the outer conductor; that is to say additional andundesirable equalizing currents over the cable cover are avoided.

The systems illustrated may also be used for matching purposes if thewave resistance of the wound transmission line 8 coincides with thegeometric mean of the internal resistances of the systems to beconnected and if furthermore its efifective length amounts toapproximately wave length.

The matching of two systems with unequal internal resistance is alsopossible with a transmission line coupling whose wave resistance isdifferent at both ends. Such a conductor, where the characteristic orWave resistance has been made variable by altering the distance betweenthe wires, is shown in Figure 3.

The invention is of course not restricted to the constructional examplesdescribed above but can be applied to various modified forms. The turnsof the coil need not necessarily be wound on an insulator. If theconductors are rigid enough they can form a freely supported coilwithout core. If the coil turns have to have a high capacity to earth,they can be wound on an earthed metal cylinder, preferably a hollowcylinder.

As is well known, the characteristic or wave impedance of a highfrequency transmission line is determined essentially by the square rootof the ratio between the distributed inductance and the distributedcapacity per unit length of the line. Accordingly, by suitablycontrolling the spacing between the wires, as shown in Figure 3, agradual transition of the impedance may be achieved from one end to theother end of the line to effect a proper impedance match with thecircuits connected to the ends of the line. Thus, in Figure 3, theimpedance of the line at its terminals ll-l2 is relatively low due tothe close 3 spacing or high distributed capacity at this point andincreases gradually towards the terminals 13-! 4. The circuits of higherand lower internal impedance are accordingly to be connected to theterminals Hi2 and ll3|4, respectively. As will be understood, theinvention is not limited to the specific example shown in the drawing.Thus, as pointed out, the turns of the coil may be self-supporting andif the coil turns, have a high capacity to ground, they may be woundupon a metallic cylinder, preferably a hollow cylinder. These and othervariationsas well as the substitution of equivalent elements for thoseshown and disclosed may b'e-made inaccordance with the broader scope andspirit of the invention as defined in the claims.

I claim:

1. A high frequency electrical system comprising a single-ended circuit,a double-ended circuit,-

and energy transfer means interposed between said circuits andconstituted by a two-wire transmission .line of a lengthof the orderequal to at least one quarter of the length of the operating wave andwound into a double threaded spiral with the pitch of said spiralgradually varying fromone end to the opposite end of the line, said linehaving its input ends connected to one of said circuits and having itsoutput ends connectedto the other circuit.

2; A high frequency electrical system comprising a first circuit havinga pair of terminals carrying potentials symmetrical with respect toground it said circuit is excited by high frequency energy, a secondcircuit having a pair of terminals one of which is at ground potential,and energy transfer means consisting of t a two-wire transmision lineconnecting said circuits, said line having a length at least equal to aquarter of the length of the operating wave and being wound into adouble-threaded spiral with the pitch of said spiral increasinggradually from one end to the opposite end of the line and in adirection from the-circuit of relatively low internal impedance to thecircuit of relatively high internal impedance.

GUSTAV GUANELLA.

REFERENCES CITED Thewfollowing references are of record in the fil'e ofthis patent:

UNITED STATES PATENTS

